Below is a list of reputable glossaries for key terminology that will enable you to better understand what the client is asking for when you receive research in this vertical.
BPlans also has a solid glossary of terms.
Investopedia has an exhaustive list of terms with excellent explanations and is highly recommended.
Workspace is a UK-based website with a glossary.
Skeps has a glossary of financial technology terms. They do a great job of providing the newest trending jargon in banking fintech, payment fintech, sales fintech, and software & technology fintech.
The Office of the Comptroller of the Currency has a glossary of banking terms and phrases.
Pitchbook & AngelList are no longer free, but you can access some basic information with an X-ray search of the website. For example, pitchbook.com: Wonder will give these results.